An image forming apparatus (for example, which is a digital copying machine) includes a sheet conveying apparatus(es). As a sheet conveying apparatus provided for transporting a document, an automatic document feeding apparatus (ADF) is provided in the image forming apparatus. The automatic document feeding apparatus (ADF) (i) receives a document from a placement tray, (ii) transports the document to a reading (scanning) section, and (iii), after an image on the document is read out, delivers the document to a delivery tray. On the other hand, as a sheet conveying apparatus provided for transporting a printing sheet, a paper feeding conveying mechanism is provided in the image forming apparatus. The paper feeding conveying mechanism (i) receives a sheet from a paper feeding cassette, (ii) transports the sheet to an image forming section, and (iii), after an image is formed on the sheet by the image forming section, delivers the sheet to a delivery tray.
According to the sheet conveying apparatus of the above type, a pickup roller picks up one sheet at a time from the placement tray storing a stack of sheets such as documents, paper, or the like. Thereafter, the sheet is transported by a plurality of conveyance roller pairs provided to a sheet conveyance path, and then delivered to a delivery tray. The sheet conveyance path includes a conveyance guide for guiding the sheet. The plurality of conveyance roller pairs are provided along the conveyance guide.
Patent Literatures 1 through 3 disclose automatic document feeding apparatuses each including two delivery trays. In each of such automatic document feeding apparatuses, a paper transporting path (hereinafter referred to as a path) being extended downstream of a reading section branches into (i) a straight conveyance path and (ii) a U-turned conveyance path, (i) the straight conveyance path being extended straight in a conveying direction of a document being passed through the reading section, and (ii) the U-turned conveyance path having a U-turn shape so that a conveying direction of a document passed through the reading section is u-turned upwardly and backwardly. Therefore, a destination to which a document is delivered can be switched between the two delivery trays.
The document being transported via the straight conveyance path is delivered to the delivery tray which is outwardly extended from a lateral side of the automatic document feeding apparatus. On the other hand, the document being transported via the U-turned conveyance path is delivered to the delivery tray which is provided above a document placement tray.
Conventionally, switching of the destination between the delivery trays is carried out by a configuration which includes, at a branch between the straight conveyance path and the U-turned conveyance path, a conveyance-path switching section including a gate (branch nail), a solenoid, and the like. A control section causes a gate position to be switched from one to another, so that the document is sent to either the straight conveyance path or the U-turned conveyance path, and then delivered to corresponding one of the deliver tray provided at downstream in the conveying direction or the delivery tray provided above the document placement tray.
Patent Literature 1 teaches an art in which such switching is carried out according to a thickness of a document. This is because in a case where a document (such as a catalog or the like) not thinner than a certain thickness is fed into a U-turned conveyance path, the document may have a curling tendency, and/or jamming by the document is caused. In view of this, Patent Literature 1 delivers a thin document, i.e., a normal document, via the U-turned conveyance path, and a thick document via a straight conveyance path.
Patent Literature 4 discloses an automatic document feeding apparatus, which solely includes (i) a U-turned conveyance path and (ii), as a delivery tray, a delivery tray provided above a document placement tray. The delivery tray provided above the document placement tray has a merit that causes no increase in an installation space, as compared to a case with a delivery tray extended outwardly to a lateral side.
Furthermore, recent wide spread use of an image filing technique contributes to a development of an automatic document feeding apparatus which allows for image reading (scanning) of a document smaller than a normal document of any size from A5 to A3, such as a business card, a member ID card, or the like. There has been an increasing demand that a paper feeding conveying mechanism for transporting a printing sheet carries out (i) transporting a recording sheet smaller than a normal recording sheet of any size from A5 to A3, i.e., a recording sheet having a size of a business card, a member ID card, or the like, and (ii) delivering the recording sheet after an image formation is carried out onto it.